Services rendered (FY08 activities): 24-hr energy expenditure by whole-room respiratory chambers (181), resting energy expenditure by metabolic carts (244), exercise and physical function testing (139), body composition (270 Bod Pod measurements, 369 iDXA scans), objective physical activity monitoring (451), muscle biopsies (40), subcutaneous fat biopsies (40), and Health and Physical Exams (35). Research findings: In 25 young and normal-weight healthy volunteers, Dr. Francesco Celi and his colleagues have found that a 12-hr environmental temperature change (from 24 to 19 C) produced a 6% increase in resting energy expenditure as measured by our metabolic suites. This increase was likely a result of the activation of brown adipose tissue via the sympathetic nervous system, but less of an influence by the thyroid hormone. A manuscript is in preparation and expanded studies are underway to study obese and elderly individuals and to further quantify the brown adipose tissue activity by FDG-PET imaging. Dr. Rana Malek and her colleagues have discovered that neck circumference in 115 heterogeneous study volunteers (BMI 18-63 kg/m2) was a good predictor of insulin sensitivity, and better predicted metabolic syndrome status in women than waist circumference. Further study in various racial and ethnic groups is planned and a manuscript is in review. We are also developing an intra/extramural collaboration project with Dr. Naji Abumrad from Vanderbilt University to study the changes in energy metabolism, protein turnover, insulin action, and associated weight loss before and after Roux-en-Y gastric bypass surgery. We expect this study will help us understand the dynamic responses of the endocrine system and its impact on whole-body metabolism during rapid weight loss.